Rob irregular corporal of horse (6)
I believe the answer is:
bronco
'horse' is the definition.
(bronco is a kind of horse)
'rob irregular corporal' is the wordplay.
'irregular' is an anagram indicator.
'corporal' becomes 'nco'.
'rob' is an anagram of 'bro'.
'bro'+'nco'='BRONCO'
'of' acts as a link.
(Other definitions for bronco that I've seen before include "American wild horse" , "Wild horse of the West" , "Half-tamed horse used in rodeos" , "An unbroken mustang, bucking perhaps" , "Wild bucking horse" .)